tax-calculation

Install the taxjar npm package, initialize it with an API key from environment variables, and call taxForOrder with from/to addresses, line items, and shipping cost. After payment confirmation, call createOrder to commit the transaction for filing reports.

Both provide real-time calculation and filing reports with native Shopify, WooCommerce, and BigCommerce integrations. Avalara AvaTax covers more international jurisdictions, while TaxJar is commonly chosen for US-focused compliance; Stripe Tax is simplest for Stripe-based stores.

For cross-border EU B2B sales, validate the buyer's VAT number via the EU VIES REST API before applying zero-rate reverse charge. If validation fails, charge VAT at the destination country's B2C rate instead.

You need nexus in the state: physical presence like warehouses or employees, or economic nexus triggered at $100,000 in annual sales or 200 transactions in most states. California and Texas use a $500,000 threshold.

Apply a fallback rate such as the US average of approximately 8.5% rather than blocking checkout entirely. For custom builds, cache tax estimates by destination zip code and cart total for one hour to reduce latency and API dependency.

Tax transactions must be committed after payment is confirmed, not during estimation. Verify your TaxJar or Avalara plugin is configured to auto-commit on order completion, and void transactions when refunds are issued.